The present invention relates, in general, to electric motors and, more specifically, to electric motors used in vehicle engine cooling fan assemblies.
Many vehicles use cooling fan assemblies driven by electric motors to provide cooling airflow for the radiator to control engine coolant temperatures and for the condenser which is part of the cabin air conditioning system. The cooling fan assembly and motor is typically located in the underhood environment immediately behind the radiator and condenser module. The underhood environment is very harsh with exposure to high temperatures, road debris, water spray and other environmental hazards. The engine cooling motor must operate in this harsh environment. Component temperatures inside the motor must be held below respective maximum levels to allow the motor to meet its performance and durability requirements. The motor must also survive exposure to water and other abuse factors and continue to operate in a normal manner.
The desire to control motor component temperatures and to enable the motor to survive in the harsh environment present conflicting design requirements. Motor component temperatures are often controlled by using elements in the fan hub to draw cooling airflow through the inside structure of motor itself The airflow removes heat from inside the motor and provides a means to control component temperatures.
A motor designed to allow cooling airflow to pass through the motor will also most likely allow entry of water and other contaminants that may damage the motor. Motor designs to limit water entry usually significantly reduce the volume of cooling airflow through the motor. Such designs typically provide constricted openings into the interior of the motor case. The small throat size of such openings impedes water entry while still providing a small amount of cooling airflow through the motor. Interior baffles or deflectors may also be mounted within the motor case across the small openings to limit the amount of water entry into the motor.
Designs to totally seal the motors against intrusion of both water and/or cooling airflow severely limit the power capability of the motor frame size thereby resulting in much lower wattage rated motors. Lower ratings can be increased through the use of more expensive higher temperature rated materials, insulation, winding and the like. And, for continuous operation, a suitable means or heat sink to carry heat away from the fan motor itself may be provided; but again, at a much higher cost.
Therefore, it has become a typical practice to provide air circulation apertures in the end bell or end wall of the drive motor case at a position closely adjacent to the fan blade hub. When water is sprayed up from the wheels or is entrained in the air, it may enter the motor through the ventilating openings. However, suitably positioned drain holes allow any water which may enter the motor to escape without collecting and presenting a potential for damage to the motor.
Thus, it would be desirable to provide a vehicle engine cooling fan drive motor having a design which incorporates ventilation opening but which prevents water entry into the motor. It would also be desirable to provide a vehicle engine cooling fan drive motor which, at the same time, provides enhanced cooling flow through the motor. It would also be desirable to provide a vehicle engine cooling fan drive motor which provides the above capabilities with minimal modification to existing motor designs. It would also be desirable to provide a vehicle engine cooling drive motor which provides the above capabilities while easily accommodating different motor blade and fan hub sizes and shapes.